Abdur Rahman bin Wahla (may Allah have mercy on him) said to Sayyiduna Ibn Abbas (may Allah be pleased with them): "Indeed, when we go for jihad, leather and water skins are brought to us." He replied: "I do not understand what I should say to you, but I have heard the Messenger of Allah (peace and blessings be upon him) say: 'Any leather that is tanned, indeed, it becomes pure.'"